The National Theater no longer is included in plans for the complex planned by the National Press Club Building Corp. and Atlanta architect-developer John C. Portman.

Originally a new theater was included in plans announced in September for the complex on the block between E and F Streets and 13th and 14th Streets. The present building could be razed as early as two years from now or five at the outside.

The site at 1321 E St. NW has been the location for five theaters since the first was opened 142 years ago, an anniversary celebrated last night.

The deletion appears to have resulted from a meeting held six weeks ago in the office of lawyer Maurice B. Tobin. Present were Tobin, president of the New National Theater Corp., which controls the present theater; several of its officers and trustees; National Press Club President Robert E. Farrel, and representatives of Portman and Roger L. Stevens, the Kennedy Center chairman, whose office books attractions for the National.

To include a theater with offices above the stage "fly" space, which has been done in several New York buildings, the Portman people stated would cost "many millions of dollars," according to Farrell.

Both Tobin and Stevens agreed that such sums, over $10 million, would be impossible for the nonprofit National Theater Corp. to raise. Furthermore, it would cost about $300,000 annually for unkeep and expenses. Such figures are far beyond the National's present means, said Tobin.

The National corporation has "an ironclad" 20-year lease on the building with around 18 years to run; but legally condemnation proceedings could break that contract, freeing the site for the complex.

In the event of condemnation, the money would go to the National board, and efforts would be made to locate some land for a new building through the Pennsylvania Avenue Development Corp according to Tobin. The purchase money would help finance a new theater building.

Stevens, who is not a member of National's board, appeared amenable to this and is known to want more stages in the city for productions often locked out of Washington's crowded booking schedule.

Tobin, however cites the location's historical appeal. Only two other theaters in this country have had so long a tenure on the same sites, Philadelphia's Walnut Street and Charleston's Dock Street "Away from E street, we might as well be in Dubuque," he said.

Theater costs are gauged on the basis of cost-per seat, explained the Kennedy Center's general manager of theaters, Alexander Morr. "The ballpark figure mentioned in early discussions was about $3,000 per seat, and we think in terms of at least the present $1,680. Milwaukee's new performing arts center and the Pittsburgh Heinz Hall are figured at about $3,500 per seat, but the Chandler Pavilion, in Los Angeles, cost over $6,000 a seat and the Metropolitan was at least $12,000. This is an expensive city, and I'm afraid it would run well over that $3,000 discussed.

"But," Morr said "all the figures under discussion were ballpark figures. No one really knows, except that at present the National has nothing like such funds for building purposes."

The present National, 55 years old and fifth theater on the site, has had a varied existence. It is booked through the Kennedy Center under a management-services contract, which costs the theater $25,000 a year. In the past year, bookings have been increasingly profitable, and plans have been made for considerable refurbishing.

Future bookings, said Morr, include at least three long-run situations that "will keep the stage full into the fall of 1979."

The Press Club's Farrell said yesterday that the club's board still hopes the National's trustees will come up with a solution, because, "The club wants the theater in the new complex and has no desire to break the site's theatrical tradition. But that will cost money."

National board member Roy O. Harris Jr. is convinced that a public campaign to preserve the location would be successful, though he was less sanguine about the fund raising."Nobody now has even a definite figure to shoot for," he said.

An informal party was held in the National's mezzanine lobby yesterday marking the 142d anniversary. A toast was offered to the first stage attraction at the site. "The Man of tix World," and star James Earl Jones offered another to its current attration "Paul Robeson."